Removed unnecessary and/or obsolete GC hacks

the intent of these hacks was to break cyclic references to avoid having objects lingering in memory. However, all of the stuff that's being removed in this commit no longer has any effect anyway, due to the fact that these things don't circularly reference each other anymore. Notably, Tile inventories now keep Position instead of a Tile ref.

src/entity/Entity.php

@@ -1587,7 +1587,6 @@ abstract class Entity{
 	 * It is expected that the object is unusable after this is called.
 	 */
 	protected function destroyCycles() : void{
-		$this->location = null;
 		$this->lastDamageCause = null;
 	}